Optimization of molybdenum-doped Ni-rich layered cathodes for long-term cycling

Abstract

The doping of Ni-rich layered cathodes is an indispensable strategy for addressing their poor ability to support long-term cycling. However, the effect of dopants on the properties of cathode materials is difficult to predict, complicating the development of cathodes with optimized electrochemical performance. This study investigates the effect of dopant (Mo) content and lithiation temperature on the properties of a Ni-rich layered cathode material and electrochemical performance of the resulting cathode. The presence of sufficient Mo affords cathode materials with fine primary particles over a wide lithiation temperature range and increases the temperature at which their crystal structures form during lithiation. It is demonstrated that the electrochemical performance of Mo-doped Ni-rich layered cathodes is largely determined by the secondary particle morphology (primary particle size) and crystallinity of the cathode material. Higher crystallinity and finer primary particles correspond to higher capacity and better long-term cycling performance, respectively. The empirically optimized Mo-doped Ni-rich cathode developed in this study, which is based on a cathode material featuring fine and appropriately crystalline primary particles, is sufficiently mechanically and structurally stable to afford Li-ion batteries with a long cycle life.